[PATCH] Inline C99 math functions

[Joseph Myers]

On Mon, 15 Jun 2015, Wilco Dijkstra wrote:

> Add inlining of the C99 math functions 
> isinf/isnan/signbit/isfinite/isnormal/fpclassify using GCC built-ins 
> when available. Since going through the PLT is expensive for these small 
> functions, inlining results in major speedups (about 7x on Cortex-A57 
> for isinf). The GCC built-ins are not correct if signalling NaN support 

Where are the benchmarks for this?  Please put them in benchtests so 
actual reproducible figures can be given.  That's the standard practice 
for any change being justified on the basis of performance.

What are the effects on code size (especially for fpclassify)?  If code 
becomes larger, conditioning on !defined __OPTIMIZE_SIZE__ should be 
considered.

> As a result of this many target overrides and the various 
> __isnan/__finite inlines in math_private.h are no longer required. If 
> agreed we could remove all this code and only keep the generic 
> definition of isinf/etc which will use the builtin.

How do those inlines compare with the code GCC generates?  As I understand 
it, before your patch libm-internal calls to these macros would have 
called the inline versions of functions such as __finite (no function 
call, PLT or otherwise, and using integer arithmetic), and after the patch 
libm-internal calls would have used the GCC inlines (with floating-point 
arithmetic) - is the new state for libm-internal calls better than the old 
state or not?

> 2015-06-15  Wilco Dijkstra  <wdijkstr@arm.com>
> 

	[BZ #15367]
	[BZ #17441]

-- 
Joseph S. Myers
joseph@codesourcery.com